In recent years, thin, light, and low-power-consumption display devices such as liquid crystal display devices have been remarkably widespread. Typical examples of apparatuses on which such display devices are mounted encompass mobile phones, smartphones, notebook-sized personal computers (PCs), and the like. It is expected that, in the future, development and prevalence of electronic paper, which is an even thinner display device, will be rapidly advanced. Under such circumstances, it is a common challenge to reduce power consumption of display devices.
According to conventional continuous grain (CG) silicon thin film transistor (TFT) liquid crystal display panels, amorphous silicon TFT liquid crystal display panels, and the like, it is necessary to refresh a screen at 60 Hz. Therefore, for a reduction in electronic power consumption of the conventional liquid crystal display panels, attempts have been made to achieve a refresh rate lower than 60 Hz.
In recent years, diligent attempts have been made to develop an oxide semiconductor liquid crystal display panel in which TFTs are each constituted by an oxide semiconductor that uses indium (In), gallium (Ga), and zinc (Zn). According to a TFT constituted by an oxide semiconductor, only a small amount of electric current leaks in an off state. Therefore, unlike the cases of conventional liquid crystal panels, it is unnecessary for an oxide semiconductor liquid crystal display panel to refresh a screen at 60 Hz, and it is therefore possible to lower a refresh rate to approximately 1 Hz. This allows for a reduction in electric power consumption.